Compressor



Dec. 26, 1950 s. A. J. MANSTED 2,535,308

' COMPRESSOR' Filed Oct. 15, 1949 INVENTOR Jbemldz'ehZIymJlwwZaL BY f 46 ATTORNEYS,

Patented Dec. 26, 1950 UNITED STATES i ATENT O F Fl CE COMPRESSOR Svend Axel Jorgen Mansted, Hellerup, near Copenhagen, Denmark Application October 13, 1949, Serial No. 121,116 In Denmark November 10, 1947 4 Claims. (01. 230-29) whereby a complete balancing of the mass forces is obtained and thereby a smooth and non-vibratory working, but the construction has other serious drawbacks.

By way of example, the production of the curved path is extensive and difficult, and a considerable loss due to friction asserts itself during the operation because the friction between the outwards-projecting piston ends and the curved path has a long moment arm to act upon. Finally a piston which is restrained in its motion by accidental obstructions, such as impurities or a slight jamming in the cylinder, may get stuck in its innermost position, which will give rise to heavy vibrations on account of the lack of balance.

Compressors of this type are also known where instead of being driven by a curved path provided around the cylinder block the pistons are connected to an eccentric device provided around the axis of rotation, so that all the pistons are made to rotate in an almost circular path situated eccentrically in relation to the axis of rotation.

This, however, requires that each piston work in a separate cylinder, whereby the total clearance becomes larger than in the case of pair-wise opposed pistons working in. a common cylinder, and furthermore the automatic and complete balancing of the mass forces attained by the pistons working exactly opposedly will be lost. Moreover, the whole of the effective stroke is to be provided by a single eccentric, the diameter of which must, therefore, be comparatively large in order that the eccentric sheave have a suitable position in relation to the axis of rotation, which entails an unnecessarily large loss by friction.

Such compressors with eccentric-driven pistons are also known in embodiments with two oppositely directed eccentric devices which cause the pistons to work in counterphase, but these known constructions are not satsfactory in other respects. By way of example, the eccentric sheaves are of a considerable size, and each piston works in a separate cylinder, while at the same time the construction necessitates the use of a complicated valve arrangement for the control 2 of the admission and outlet of the working" medium.

The'purposeof the present invention is todesign an improved construction of'a compressor of the kind stated, in which the advantages ofthe known embodiments are united while their drawbacks are avoided, and'with this purpose in view the construction consists in thefoll'owing combienation of constructive featuresknown per s'e, viz.

that the pistons -work by twos in a common through-going cylinder bore, that thepistons are driven in counter-phase by stationary, oppositely directed eccentrics which are mounted at the axis of rotation with the eccentric rods connectedto the'pistons at the outer ends of the'latter,-and thatthe slide valvemechanism serving for the-control of theadmission and exhaust-of the workingmedium consists of a channelopening'out on one side surface of the cylinder block at some distance from the axis of rotation, which channel co-operates with an annular slide valve face provided at right angles to the axis-of rotation.

Bythis combination a compressor is obtained with-pistonsthat are opposed in-the proper sense of the wordandare driven by a driving mech anism with the least possible frictionlosses and with a completely automatic balancing ofthe mass forces, while at thesame time the slide valve mechanism is extremely easy to produce and seal and demands no increase in the diameter -of the cylinder block or eccentric sheaves. The compressor can, therefore, have the smallest possible dimensions fora given effect and which also is suited for being operated at a high rate of revolution, and the loss caused by friction will be the least possible. There is no risk of irregularities in the operation caused by wear and tear of the slide valve mechanism or failing piston motion, and the construction is as a whole simple and strong.

The invention is illustrated on the drawing on which:

Fig. 1 is a longitudinal section on line I-I in Fig. 2 of an embodiment of a compressor in ac-' cordance with the invention, and

Fig. 2 is a section on line II-II in Fig. 1.

On the drawing, i designates the casing o'f the compressor, which casing is at the top closed by a cover 2 with a stuffing-box, not shown, for the driving shaft 3 of the cylinder block. Instead of providing the compressor with a stuffing boxit is also possible to build the compressor'together with an enclosed electro-motor, so that at herrne'ti'callysealed machine i'spr'oduced. The-cylinder block 4 proper is in one piece with the drivin shaft 3 and extends transversely to the latter and its extension 6. The driving shaft and its extension are journalled in sleeves 5 inserted in the cover 2 and a diaphragm I mounted in the casing, respectively. The extension 6 extends down into the lower part 8 of the casing where it drives a lubricating oil pump H which distributes lubricating oil to the different movable parts from a lubricating oil supply provided in the lower part.

On each of the sleeves 5, two eccentric sheaves l5 and I6 have been formed with the same eccentricity in relation to the axis of rotation and displaced 180 in relation to each other in such a way that together the four eccentric sheaves form two oppositely directed eccentrics.

The eccentric sheaves are in the usual way enclosed by eccentric straps which through eccentric rods 2'.! and 2|, respectively, are connected to transverse pins 22 on the outer ends of a pair of opposed pi tons 18 and I9 which work in the common cylinder bore. The transverse p ns 22 slide with a suitable clearance in slot 23 in the out r cy inder ends.

Fr m the midd e of the cylinder bore extends an oblidue bore 3| which serv s for the admission and exhaust of the work ng medium and wh ch opens o t on th lower ide of the c linder block in a slide valve face wh h surrounds the ext n ion 5 and co-o rates with the u r end surface, sh ped as slide va ve face, of the l er sleeve 5. In the latter th re have bv mil ing or in some other suitab e wav been pro ided a suct on chamb r 9 and a re ure chamb r IQ which are in communication with the suction c annel l of the compre or and its r ure ch nnel I2, respe tively. From the m ddle of lhP cvlinrier born t ere furth rmore eads a 'hflfg 2 le din to the int r r o the com re sor casine, th external mouth of which bore forms a seat for a val e 24 mounted on one side of a souare frame 2. The two other ides o the latter are guided in bores in the cylinder b ock and carried fr ely throu h suitable lots so in the p stons. O o ite to the val e 24 the frame oarries a mass 28, and b t e n the cy ind r block and the frame, springs 2 are in erted which tend to keep the valve 24 in its open po ition. Adjacent to the valve 24, load n bodie 29 are mounted on the cylinder block which bodies are so adjusted that the unit con i ting of cylinder block, valve, frame, sprin s and mass is balanced around the axis of rotation when the valve 24 is closed.

The mode of operation of the compressor shown appears dir ctly from the drawin When the cylinder block is rotated in the direction indicated by an arrow in Fig. 2 from the po ition shown, the pi tons l8 and [9 wil ap ro ch each oth r and compress the working medium which is discharged through the pressure channel l2, when the mouth of th bore 3! sweeps across the pressure chamber Ill. The pi tons are arranged for approaching each other as closely as mech nically feasible and thereby the clearance is reduced to a minimum and con ists in fact only of the bore 3| proper. During the continued rotation, the pistons are driven outwards again, while the mouth of the bore 3| sweeps across the suction chamb r 9 so that a new charge is sucked into the cylinder.

The valve 24 is kept closed on account of the centrifugal force acting on the mass 28, and the:

whole movable system is completely balanced statically and dynamically.

Only durin rest and start are the springs 21 strong enough for keeping the valve 24 open so that no compression can take place in the cylinder. Starting is thereby facilitated, and as soon as the cylinder block has obtained a certain rotary velocity, the centrifugal force on the rotary mass 28 will overcome the springs 21 and close the valve 24 so that the compressor can start working, and at the same time the complete balance is established.

The invention is not limited to the embodiment shown and described. In the same compressor there may be several cylinder bores e. g. placed successively in. the direction of the axis of rotation and working with a suitable mutual phase displacement or in several stages. The working space need not necessarily lie symmetrically around the axis of rotation of the cylinder block, but may be displaced to cne side or the other in the direction of the axis of the cylinder bore. The pistonswith associated ports-need not have the same weight and stroke. essential feature is only that the weight and stroke of related pistons are chosen in such a manner that the forces will substantially balance each other outwardly.

The invention may be app-lied in compressors of different sizes and outputs. and for different Working media. It is especially suited for small and medium-size highpeed. fully-enclosed compressors for refrigerating plants.

I claim:

1. An opposed-piston compressor comprising a cylinder block journailed for revolution around an axis and having a through-going cylinder bore perpendicular to said axis of revolution, a pair of opposed pistons in said cylinder bore, oppositely directed stationary eccentric means positioned in the vicinity of said axis of revolution, eccentric rods operatively connecting either of said pistons to one of said eccentri means respectively, each rod being pivotally connected to the pertaining piston in the vicinity of the outer end therecf, a conduit emerging from the cylinder space confined between the opposed piston surfaces and openingout on one side surface of said cylinder block, and a stationary annular slide valve face concentric with the axis of revolution for cooperation with said conduit opening.

2. An opposed-piston compressor comprising a cylinder block journalled fo revolution around an axis and having a through-going cylinder bore perpendicular to said axis of revolution, a pair of opposed pistons in said cylinder bore. oppositely directed stationary eccentric means positioned in the vicinity of said axis of revolution, eccentric rods operatively connecting either of said pistons to one of said eccentric means respectively, each rod being pivotally ccnnected to the pertaining piston in the vicinity of the outer end thereof, a conduit emerging from the cylinder space confined between the opposed piston surfaces and opening out on one side surface of said cylinder block, and a staticnary ann lar slide valve face concentric with the axis of revolution for cooperation with said conduit opening, a relief valve device comprising a frame having two substantially parallel opposed sides, bores in said cylinder block transversely through the cylinder at right angies t:- the axis of revolution, transverse slots in the pistons in line with said bores, said frame sides extending through said cores and slots, a third frame side interconnecting said two frame sides and carrying a valve member, a conduit leading from the cylinder working space and opening out on the outer surface of the cylinder block in a point opposite said valve member and forming a seating therefor, a, fourth frame side situated beyond the cylinder block and said third frame side and being loaded so as to urge the entire frame under the influence of centrifugal force into a position in which said valve member is seated against the opening of said conduit.

3. An opposed-piston compressor as claimed in claim 2 and including opening springs for the relief valve mounted around the two first-mentioned opposed frame sides so as to lie compressed 6 between the cylinder block and the frame side carrying the valve member.

4. An opposed-piston compressor as claimed in claim 2, and a unilateral load on the cylinder block adapted in such a manner as regards weight and position in relation to the loadon said fourth frame side as to counter-balance the latter statically and dynamically when the movable frame structure is in the position in which the valve member is seated against the opening of said conduit.

SVEND AXEL JRGEN MANSTED.

No references cited. 

